Assessment of ancient masonry slender towers under seismic loading: dynamic characterization of the Cuatrovitas tower

The Cuatrovitas tower is a XIIth century almohad minaret located in the province of Seville (Spain) and it is considered the best preserved almohad religious building in the Iberian Peninsula. As it is placed in a seismic area, it is crucial for its preservation to evaluate its dynamic response under earthquake loading and to assess the safety level in its present state of conservation. In this paper a number of three-dimensional linear and non-linear finite element models with different levels of complexity and simplifications are developed, using 3-D solid elements or 3-D beams elements. All the models assume that the masonry structure is homogeneous and the material non-linear behaviour - including crushing and cracking - is simulated by means of different constitutive models. Subsequent non-linear static and non-linear dynamic analyses are performed. Previous static and time-history dynamic analyses with a simplified elastic material model are evaluated to calibrate the non-linear response, and to take into account that crack opening may introduce numerical instabilities. Comparison among the different models is thoroughly discussed, in particular as predicted local and global collapse mechanisms are concerned, in order to evaluate the suitability, accuracy and limitations of each analysis. To conclude, a general methodology is proposed to assess safety and to improve seismic resistance of this and other similar cultural heritage buildings.